The present invention relates to an information terminal capable of exchanging messages via a network, and also to a server and a program for providing a service required by the information terminal for exchange of messages.
With the recent diffusion of the Internet, there is noticed an increase in the number of users who transfer various data to and/or from partners through the Internet. A known system adapted for such transfer of data is, for example, an IM (Instant Messaging) system which transfers text information via the Internet and performs communication in real time with partners.
In the conventional IM system, at the time of connection via the Internet, there are automatically displayed, on the terminal screen in use, the state of connection of a pre-registered partner to the Internet, and any message from the partner, wherein messages are exchanged in real time, or a chat or file is sent (e.g., as described in Cited non-patent reference 1).
Also in the IM system, personal information of each user registered in an IM server is provided for some other user who is in a formed relation of exchange. For example, in case a user A and a user B have formed a relation of exchange, the user B is registered as a buddy of the user A on a buddy list for the user A, while the user A is registered as a buddy of the user B on a buddy list for the user B.
In forming a relation of exchange, one user (e.g., user A) transmits an “invitation” to the other user (e.g., user B), and the user B having received the “invitation” transmits a “consent” in the case of accepting the “invitation” from the user A (i.e., in the case of forming a relation of exchange).
When the user A invites the user B, it is necessary for the user A to know the ID of the user B. And when the user B sends a “consent” to the user A, it is necessary for the user B to know the ID of the user A. For acquiring the ID, both persons negotiate directly with each other to tell the respective ID mutually.
In another known method, the personal information of each user is saved in the IM server, and one user as a searching person searches the ID of the other user who is an interesting target person for the searching user, and the result of such a search is sent as a reply to the terminal of the searching person. More specifically, a search condition is given from the terminal of the searching user to the IM server, so that the IM server can collate the given search condition with the personal information of each user to thereby find out some user who satisfies the given search condition.
[Cited Non-patent Reference 1]
Digital Creators Liaison Conference, Multimedia Internet Dictionary, “Instant Messaging”, [online], [Searched Aug. 4, 2003], Internet, <URL:    http://www.kaigisho.ne.jp/literacy/midic/data/k2/k2122.ht m>
However, in the conventional search system, the information that satisfies the search condition is retrieved, at the time of input of the search condition by the searching user, from the personal information stored in the database of the IM server, and then the retrieved personal information is sent to the searching user. Therefore, even in case the personal information in the database of the IM server is changeable in real time, if the result of the search has once been sent to the searching user, the updated contents of the database are not reflected on the search result given to the searching user. Thus, there arises a problem that, if some user adapted for satisfying the search condition has appeared after execution of the search, the searching user fails to be notified of the fact.
Moreover, since all searches are executed wholly in the IM server, loads are concentrated on the IM server so that, particularly at a time of congestion, there may occur a fall of the reply efficiency as viewed from the searching users.